title: Woody clockworks: circadian regulation of night-time water use in Eucalyptus globulus.
abstract: The role of the circadian clock in controlling the metabolism of entire trees has seldom been considered. We tested whether the clock influences nocturnal whole-tree water use. Whole-tree chambers allowed the control of environmental variables (temperature, relative humidity). Night-time stomatal conductance (gs ) and sap flow (Q) were monitored in 6- to 8-m-tall Eucalyptus globulus trees during nights when environmental variables were kept constant, and also when conditions varied with time. Artificial neural networks were used to quantify the relative importance of circadian regulation of gs and Q. Under a constant environment, gs and Q declined from 0 to 6 h after dusk, but increased from 6 to 12 h after dusk. While the initial decline could be attributed to multiple processes, the subsequent increase is most consistent with circadian regulation of gs and Q. We conclude that endogenous regulation of gs is an important driver of night-time Q under natural environmental variability. The proportion of nocturnal Q variation associated with circadian regulation (23-56%) was comparable to that attributed to vapor pressure deficit variation (25-58%). This study contributes to our understanding of the linkages between molecular and cellular processes related to circadian regulation, and whole-tree processes related to ecosystem gas exchange in the field.
authors.affiliation: Hawkesbury Institute for the Environment, University of Western Sydney, Richmond, NSW, 2753, Australia.
authors.forename: Víctor
authors.initials: V
authors.lastname: Resco de Dios
authors.affiliation: Departamento de Física Matemática y de Fluidos, Universidad Nacional de Educación a Distancia, E 28080, Madrid, Spain.
authors.forename: Rubén
authors.initials: R
authors.lastname: Díaz-Sierra
authors.affiliation: Department of Earth System Science, University of California, Irvine, CA, 92697, USA.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Goulden
authors.affiliation: Hawkesbury Institute for the Environment, University of Western Sydney, Richmond, NSW, 2753, Australia.
authors.forename: Craig V M
authors.initials: CVM
authors.lastname: Barton
authors.affiliation: Hawkesbury Institute for the Environment, University of Western Sydney, Richmond, NSW, 2753, Australia.
authors.forename: Matthias M
authors.initials: MM
authors.lastname: Boer
authors.affiliation: Institute for Landscape Biogeochemistry, Leibniz-Centre for Agricultural Landscape Research (ZALF), 15374, Müncheberg, Germany.
authors.forename: Arthur
authors.initials: A
authors.lastname: Gessler
authors.affiliation: Department of Crop and Forest Sciences-AGROTECNIO Center, Universitat de Lleida, E 25198, Lleida, Spain.
authors.forename: Juan Pedro
authors.initials: JP
authors.lastname: Ferrio
authors.affiliation: Hawkesbury Institute for the Environment, University of Western Sydney, Richmond, NSW, 2753, Australia.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Pfautsch
authors.affiliation: Hawkesbury Institute for the Environment, University of Western Sydney, Richmond, NSW, 2753, Australia.
authors.forename: David T
authors.initials: DT
authors.lastname: Tissue
mesh_terms: D002940:Circadian Rhythm; D017753:Ecosystem; D004777:Environment; D005052:Eucalyptus / Q000502:physiology*; D054046:Plant Stomata / Q000502:physiology; D018526:Plant Transpiration; D014197:Trees / Q000502:physiology*; D014867:Water / Q000502:physiology*; D014934:Wood
chemical_list: D014867:Water
keywords: cells-to-ecosystem; circadian clock; night-time stomatal conductance; sap flux; scaling; water balance